The formal semantics of the progressive aspect is notoriously difficult to pin down, as a number of analyses in recent years attest (Dowty 1979:§3, Vlach 1981, Parsons 1990:§9, Bach 1986, Kearns 1991, Asher 1992, Landman 1992, Glasbey 1996, among others). Broadly speaking, the progressive presents two sorts of problems: (i) (what we might call) the 'state-related problem' and (ii) (what Dowty calls) the 'imperfective paradox'. […]
for the time being (until i manage to convert the old wordperfect 3 for the macintosh file into a useful format), this is a scan at 300 dpi of the published paper. unfortunately and inevitably, it's a rather big file. :-(